1. Field of the Invention
The present invention relates to the fields of telecommunications and computing. More particularly, the present invention relates to a protocol for voice-data integrated multiaccess to FDD (frequency division duplex) or TDD (time division duplex) local- or wide-area networks.
2. Description of the Related Art
The emerging convergence of telecommunications and computing has brought about considerable significance to dynamic multiplexing of voice and data over both wireline and wireless multiaccess channels, such as used in cellular and hybrid fiber-coax (HFC) networks. Bandwidth efficiency is a key consideration for voice-data integration and has been addressed in many studies by applying packet switching to both voice and data portions of the traffic, shunning circuit switching altogether.
For conventional multiple access, speech packets generated during active speech periods contend for channel access in a manner similar to that used for data packets, for instance, on Ethernet LANs. Packet reservation multiple access (PRMA) and derivatives of PRMA, as well as D-TDMA, are the most familiar medium access control (MAC) protocol examples that operate on this basis. Nevertheless, speech packets may encounter excessive delays for conventional multiple access, thereby resulting in speech clipping.
As is well known, bandwidth efficiency is not the only issue that merits attention in packet transmission. Quality of service is another critical factor that must be taken into account to meet the requirements of the underlying applications. In this regard, speech transmission delay should be always upper-bounded to a certain threshold for a satisfactory reception.
What is needed is a technique for dynamically multiplexing voice and data over a multiaccess channel that provides a predetermined quality of service for voice transmission by providing a speech access delay that is always upper bounded to a predetermined threshold.
The present invention provides a technique for dynamically multiplexing voice and data over a multiaccess channel that provides a predetermined quality of service for voice transmission by providing a speech access delay that is always upper bounded to a predetermined threshold.
The advantages of the present invention are provided by a MAC protocol that operates on an uplink and a downlink channel. The uplink channel has a plurality of frames, such that each frame has a first selectable number of minislots and a second selectable number of slots. When a user has voice traffic that is to be sent, the user sends a reservation request of a first type into a first selected minislot of a selected frame of the uplink channel using a contention-free technique. The reservation request of the first type is for requesting an assignment of at least one slot in at least one frame that is immediately subsequent to the selected frame for transmitting the voice traffic of the user. When a user has data traffic that is to be sent, the user sends a reservation request of a second type into a second selected minislot of the selected frame when such a minislot is available in the selected frame using a contention-based technique. The reservation request of the second type is for requesting an assignment of at least one slot in at least one frame that is subsequent to, but not necessarily immediately after the selected frame, for transmitting the data traffic. The rules for making a contention-based request for transmitting new or previously-colliding reservation requests of the second type by user terminals and for allocating the corresponding uplink channel resources by the central station are governed by a pseudo-Bayesian controlled Aloha algorithm or by a nonobvious blocked-access binary tree algorithm. The central station generates and sends a downlink channel feedback message prior to the end of the selected frame of the uplink channel. The feedback message contains bandwidth assignment information for the next frame of the uplink channel of minislots assigned for reservation requests of the first type, slots assigned to reservations requests of the first type received during the selected frame and, if sufficient bandwidth is available the next frame, minislots assigned for contention-based reservation requests of the second type and/or slots assigned for data traffic corresponding to reservation requests that were successfully sent in the selected frame or a frame prior to the selected frame.